The present invention relates to single engine vehicles with auxiliary hydraulic systems, such as street sweeper vehicles with rotating brushes or fan/blowers for gathering and collecting sand and other road debris.
Street sweeping vehicles, designed with either front or rear wheel drive, use a variety of brush/air configurations and other equipment for gathering up dirt and debris and conveying it to a hopper within the vehicle. These vehicles must be able to creep along at one to five miles per hour while sweeping; they must also be driven in traffic at up to fifty miles per hour to travel between job sites. Most single engine type sweepers employ a torque converter and automatic transmission to drive the vehicle wheels. The same engine also directly drives a hydraulic pump which powers the sweeping accessories and brushes either by air operated or mechanical means. The operation of the cleaning apparatus requires the engine to run at a minimum of about 1200 r.p.m. to provide adequate power to the hydraulic pump. At that rotational speed, the torque converter is fully engaged and even at the low gear range of the transmission, the vehicle brakes must be used constantly to reduce road speed to the required range. This is very wasteful of fuel and reduces the wear life of the brakes.
Several solutions to this problem have been applied. One involves the use of separate engines to drive the sweeping apparatus and the vehicle wheels. This results in increased first cost and maintenance. Another solution using a single engine involves the use of a hydrostatic drive to operate the vehicle wheels. This is expensive and fuel inefficient. Another solution provides an extra-low gear for the transmission; while workable, the enormous power provided to the wheels at sweeping speeds requires much brake force to stop the vehicle due to engine inertia.
Yet another solution disclosed in Vanderlinden (U.S. Pat. No. 6,073,720) uses a dual method of providing power to the differential driving the vehicle wheels. One method is used for sweeping while the standard transmission is used for travel between job sites. This adds cost and complexity.
It is therefore an object of the present invention to provide a single engine vehicle, such as a street sweeper with accessory rotating brushes and or fan/blower operated by an auxiliary hydraulic system, with the ability to increase engine RPM""s from a normal idle without increasing forward propulsion while the automatic transmission is in a forward advancing gear.
It is also an object of the present invention to provide a street sweeper vehicle which can effectively and vigorously rotate the street sweeping brushes/fan while maintaining the vehicle""s forward advance at a safe, low speed.
It is yet an object of the present invention to increase the engine RPM""s to a desired level for satisfactory operation of the accessory street sweeping brushes/fan while slowing down the flow of fluid through the vehicle""s transmission.
It is yet another object of the present invention to maximize engine use while reducing heat and raising the overall efficiency of the street sweeper vehicle.
It is also an object of the present invention to improve over the disadvantages of prior art street sweeper vehicles.
In keeping with these objects and others which may become apparent, the present invention provides a street sweeper vehicle by changing the torque converter used in an automatic transmission for light and heavy duty vehicles.
To overcome the shortcomings of prior art street sweepers, the present invention uses a single engine with a modified torque converter on the automatic transmission.
The torque converter of the street sweeper vehicle is modified by changing the structure and orientation angle of the internal fluid flow directional vanes, which causes the vehicle""s lock-up stall pressure to occur at higher than normal RPM""s.
The modified torque converter is designed to lock up or engage at approximately 1000 r.p.m. higher than on a standard torque converter. This will increase the horsepower and torque output of the engine for driving the sweeping apparatus without propelling the vehicle at speeds too high for the sweeping function. As engine rotational speeds increase further, the modified torque converter will engage fully and drive the vehicle at desired road speeds.